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John R. de Bruyn
Physics & Astronomy 230
(519) 661-2111 x86430
debruyn [at] uwo [dot] ca
FAX: (519) 661-2033
My research focuses the physics and applications of soft materials, including polymer-based materials, gels, granular materials, non-Newtonian fluid dynamics, biological materials, and the physics of biological systems. I am mostly an experimentalist, although I have been known to dabble in theory and numerical modeling - particularly Monte Carlo simulations.
I work on lots of other things, too, particularly related to interesting (to me) applications of physics in areas ranging from sports to wastewater treatment.
I collaborate with other researchers from my own department, from several other depratments in Science, Engineering, Medicine and Dentistry, and Health Sciences here at Western, and from other universities around the world.
A brief overview of some of my research is provided below. For more information on some of the projects we are working on, please use the menu on the left. It is hard to keep this information up-to-date! If you'd like to know more, please contact me by email.
Granular materials (like sand, for example) can behave like solids, fluids, or gases, depending on the situation. If you pour sand from a jar, it flows like a fluid, but if you stand on a pile of sand, it supports your weight like a solid would. I am interested in the analogy between granular flows and conventional fluids. To what extent does a continuum description of granular material (analogous to the Navier-Stokes equations used in fluid dynamics) describe granular flows? When do the peculiar properties of granular fluids start to matter? I do experiments on granular flows, using high-speed video and other visualization methods, to investigate these questions.
Much of our research into non-Newtonian fluids is focused on materials with a yield stress, so-called viscoplastic fluids. Yield-stress fluids are very common: examples include hair gel, mustard, shaving foam, mud, and paint. They are typically suspensions of colloidal particles in a solvent (often water). They behave as soft solids when subjected to a small shear stress, but flow like a viscous fluid when the applied stress is large enough. This interesting flow behavior is a result of small-scale structure within the fluid, resulting from, for example, interactions between the suspended particles. We are interested in studying both the bulk properties and the small scale structure of yield-stress fluids, and ultimately in understanding the link between the small and large scale physics. I also study the rheology and microstructure of a variety of other polymer materials, including polymer-nanoparticle composites.
I collaborate with colleagues on research that involves the use of physics-based ideas and techniques to study problems of interest in the life and medical science. At present we are using light scattering to investigate the effects of various proteins on the precipitation of bone minerals, and studying the forces exerted by certain cells when they adhere to a substrate.